NO310158B1 - Sleeve valve assembly, flow control device and method for stimulation of an underground formation - Google Patents

Description

The present invention generally relates to a flow control device which has a sleeve-valve arrangement which is operable by means of a switching tool. The invention has special

equal application for acid treating stimulation tools used in horizontal or other awiks wells. More specifically, the invention relates to a sleeve valve heat, flow control device and method for stimulating an underground formation as indicated in the introduction to the respective independent patent claims 1, 3, 5 and 7.

Acid treatment is a popular method of well stimulation where the porosity and/or permeability of the reservoir is increased by pumping acid into areas of a formation close to a wellbore. In some wells, more than one zone will have been perforated or exposed by an open hole completion. Because the zones will often have different permeability

ter, the acid would tend to enter the zone with the highest permeability first. However, this zone would be the one that needed the least acid. A number of mechanical methods are known for selective acid application so that the majority of the acid is placed in the zones of lower permeability. These methods include the use of ball seals that are dropped into the well to block the perforations along a zone. In addition, packing elements and plugs can be used as seals to separate zones in a formation. Unfortunately, such elastomeric elements can be unreliable, particularly at great well depths where parts of the pipe string can be held at temperatures at or above 93°C. Acid at ambient temperature pumped down into the well will cause the metallic elements in the pipe string to contract when the acid reaches these depths. As continued pumping of acid be-

appears that the formation deteriorates and the amount of acid flow increases, the contraction can be significant and lead to the loss of elastomeric seals with seal bores.

A sleeve valve or sliding side door arrangement is an effective alternative to an elastomeric seal. The use of sleeve valves for optionally opening or closing a gate is well known within the well drilling technique. Shifting tool arrangements operating the sleeve valves are known where these engage with mating profiled slots in a well pipe. Such arrangements optionally place and lock a switching tool in the matching profiled slot in a well pipe using upper and lower expansion flanges.

provided with an inner mandrel which is movable downwardly within a set of wedges to lock the wedges in an expanded and engaging position. This action connects the shear tool and the profiled grooves together until release is desired. The shearing tool can be operated by retracting the wedges when desired for release from the profiled groove using a hydraulic impact device or methods such as shearing off a shear pin or the use of a ratchet type (ratchet type) indexing system.

While arrangements such as these are useful for attaching a shift tool to a selected one

somewhere inside a well pipe, they have problems in connection with releasing the switching tool

from the tube. Shear pin arrangements cannot be reinserted or reused without

withdraw the tool from the tube to replace the cutting pins. Impact tools and ratchet hooks-jiikjcetii^ebj8rer^bjft^telijg manipulenng.a.vj"?^ #r,tidkreyen-,

Deviation wells, especially horizontal wells, increase the operational problems associated with tool operation. These problems are significant for acid stimulation tools that include

accommodates sleeve valve arrangements due to the caustic, corrosive nature of the acid.

Firstly, it is difficult to balance drilling mud hydraulically in a horizontal well. IN

a vertical well gives the drilling mud a height to balance the pressure down in the well. In a horizontal well, however, there is no fluid height to balance the pressure downhole. If acid has been incorrectly placed inside the well, such as in a part without access to formation perforations, the acid can flow back out of the well. When shifting tools are removed from a horizontal well or awiks well, the tools tend to shovel out the mud together with any residual acid. Because the production zone can be 1,524 m or so in a horizontal wellbore, it is important that the operator knows exactly the location of the stimulation tool inside the pipe string. Gravity-placed wireline devices cannot be used in these wells either. Coil pipes must be used to place switchgear-

wear correctly for operating the sleeve valve. However, coiled tubing will not structurally support the application of large compressive forces that are often used to "place" the switching arrangement inside the housing, so that the acid can safely be sent into surrounding perforations. However, the pipe can carry much greater loads in tension than in compression.

Horizontal wellbore placement systems are known which use an internal placement tool which is placed inside a housing with gates. The tool is placed inside the housing under pressure. As noted, however, there are pressure limitations for coiled tubes. It is difficult to place the stimulation tools precisely so that the acid current ports are inside the desired stimulation zone due to the tendency of the tool compo-

tend to "stack on top of each other" as they are pushed into the wellbore. On

due to the problems with hydraulic balancing of horizontal wells, incorrectly placed acid can flow back out of a horizontal wellhead or be flushed back when working

the laundry is pulled out. Therefore, it is desirable to develop a system for acid treatment of formations which avoids the problems of lost wellbore seals and allows more reliable placement of stimulation tools inside horizontal wellbores.

The invention aims to remedy the shortcomings of the known technique, and this is achieved with a sleeve valve unit, flow control device and method characterized by the features indicated in the characteristics of the respective patent claims 1, 3, 5 <p>g 7.

Advantageous embodiments of the invention are indicated in the independent patent claims.

An exemplary stimulation tool includes an internal switch string and a surrounding pipe string that can be placed inside a lined borehole. The production pipe string is assembled from a number of housing sections that include sleeve valve assemblies. The switching string includes at least one switching tool with one or more switches. Among the switches are an opening switch, closing switches, and a positioning assembly which is located on the switching tool in conjunction with associated acid injection ports such that the positioning assembly will enter a fixed-hanging engagement with a housing portion at a point where the acid injection ports come substantially flush with the acid flow ports in the surrounding housing . The switching tool will be effectively fixed in a position inside the production pipe string where the acid can communicate through the production pipe string and the well casing inside the surrounding formation. The switching tool can then be detached and moved to a new position in the pipe string where the acid treatment can be carried out in a similar way. The switching tool can be moved between several downhole locations or production zones to be stimulated without pulling the tool out of the production tubing string, which would be necessary with other arrangements such as those using shear pins. A stimulation tool constructed in accordance with the present invention is particularly applicable for acid stimulation applications in horizontal well pipes.

The sleeve valve assemblies have a sleeve valve that is axially slidable within a radially expanded portion of its surrounding housing. The sleeve valve can be operated between an open position where an associated port in the housing is open to communicate fluid, and a closed position where the port is closed against fluid communication. The radially expanded portion of the housing exhibits an inwardly extending stop shoulder at one location along its length and an annular expansion notch at another location. A part of the sleeve valve is slit longitudinally to form collars and has a radially projecting, chamfered hub. An internally tensioned C-ring is placed around the sleeve valve inside the radially expanded portion. The C-ring is initially positioned to be free to move axially along the radially expanded portion between the hub and the stop shoulder.

As the sleeve valve moves towards its open position, the hub, C-ring and stop shoulder contact each other so that the sleeve valve is held firmly against further acc.

sial movement towards the open position. A significant axial force on the sleeve valve is neces-

reverse to drop the hub past the C-ring and perform disconnection and release. If that

if it is desired to release the pla of increased axial force, the requirements Uv-glidehyseniyinges.-radially4

The positioner contacts the open sleeve valve and holds it in the open position at a

point where the acid injection port is located close to the port in the housing. When the sleeve valve reaches a position where the hub, C-ring and stop shoulder contact each other, the shift mechanism

the cloth fixed in fixed engagement with the housing so that an increased magnitude of the axial force must

the shifting tool is attached to axially detach it from the housing. The axial force is preferably applied in the form of tension. The axial force required to disengage the shifting tool is usually

show much greater than the magnitude of the force necessary to move the tool inside the housing when it is not restrained. The suddenly increased resistance to axial movement caused by the retaining engagement "places" or "sets" the shifting tool inside the housing and functions as a signal to the tool operator that the shifting tool is correctly positioned.

cert. A closing switch below the positioning unit can be used to move the sleeve valve into a closed position. Movement of the sleeve valve towards its closed position can be performed without creating a holding condition for the sleeve valve. The C-ring is moved with the hub inside the expanded portion towards and finally into the radial expansion notch where it is allowed to expand to allow the hub to move past the expansion notch.

Figures IA and IB show an example of a stimulation tool that includes sliding

viewing units placed inside a lined borehole 80.

Figures 2A and 2B show an example of a sleeve valve unit where an opening switch engages a sleeve valve in its closed position. Figure 3 shows the sleeve valve unit according to Figure 1 in an open position with the opening switch during release from the sleeve valve. Figures 4A and 4B show the sleeve valve unit according to Figure 1 in a releasably secured state with a positioning unit and sleeve valve in engagement.

Figure 5 shows the sleeve valve unit according to Figure 1 after release from restraint.

Figures 6A and 6B show the sleeve valve unit according to Figure 1 during closing with a closing shawl

the terrain.

Figure 7 shows a detail of an exemplary boss and C-ring.

Reference is first made to figures IA and IB, where a stimulation tool 40 is shown as including

ter a production pipe string 70 and a switch string 76 suspended in a lined borehole 80.

The lined borehole 80 extends through one or more hydrocarbon producing zones

85 in the surrounding formation 83. The borehole 80 is preferably a horizontal well,

although it can be any type of well including a switch well or deviation well. The term "upper" as used here shall mean in relation to the bottom 87 of the borehole 80 even though the borehole 80 may be horizontal. The switch string 76. is usually assembled from sections with pressure pipes (wash pipes) or coil pipes. Lined wellbore 80 has been perforated with perforations 82 to allow hydrocarbons to flow from the producing zones 85 into the lined wellbore 80. Due to the features described herein, the stimulation tool 40 is operable to optionally inject a stimulation fluid, such as acid , from the surface via an acid treatment mandrel 52 through the perforations 82 and into the production zones 85. The switch string 76 is connectable inside a well stream tube (not shown) through which fluids such as acid are sent. The production tubing string 70 is advantageously fitted internally with surface engagement devices 75, such as threads or notches, to engage substantially complementary engagement devices on a string of tubing 74 extending to the surface of the well. The stimulation tool 40 also includes a hinged flap valve 75 to assist in sealing the production tubing string 70 after the switch string 76 and the switch tool 60 are removed. An opening 78 is arranged at or near the lower end of the pipe string 70 for guiding well fluids as the switch string 76 is slidably placed inside the production pipe string 70. A velocity check valve 66 is placed above the valve switch 65 for well control.

In operation, the production tubing string 70 is positioned within the lined wellbore 80 such that the sleeve valve assemblies 72 are located near the perforated producing zones 85. Often, more than one sleeve valve assembly 72 will be located near each set of perforations 82 in the event that one unit becomes inoperative. Expansion seals 81 are placed on either side of the producing zones 85 to delimit and isolate the producing zones 85 during stimulation. The switching tool 60 is then mounted inside the production pipe string 70 and axially movable in this. An opening 78 vents well fluids to prevent a hydraulic lock of the switch string 76 when the string 76 is moved within the tubing string 70. The switches along the length of the switch tool 70 include the opening switch 62, the location assembly 63, the closing switch 64 and the valve switch 65 for well control. The sleeve valve assemblies 72 along the length of the production tubing string 70 contain a number of ports 115. As noted, the ports 115 are advantageously located near the perforations 82 and are adapted to allow fluid communication to occur between the interior of the production tubing string 70 and its exterior. As will be described in more detail below, the ports 115 are activatable with the sleeve valve assembly 72 and the switches 62, 64. The production tubing string 70 includes sections of the casing 101 (shown in Figure 2). The switch string 76 includes one or more switch tools 60 along its length and a velocity check valve 66 near the lower end. A section of the housing 101 and 101 and the switch tool 60 together form a flow control device 50, which can optionally place fluids placed through the well flow pipes and into the producing zones 85 as desired. In order to control optional placement, the flow control device 50 includes one or more sleeve valve units 72 whose function and operation will be briefly described. Exemplary switch tool 60 includes a number of switches 62, 63, 64 and 65, an acid treatment mandrel 52 with O-rings 61 on each side thereof.

Reference is now made to Figures 2-7, where an exemplary sleeve valve unit 100 of the many sleeve valve units 72 is shown in greater detail. The sleeve valve assembly 100 includes a substantially cylindrical outer housing 101 which is serially connected and laid as part of the pipe string 70 and includes an inner fluid flow pipe 102 formed by the inner cylindrical surface 103 of the housing 101. The housing 101 is formed by an upper pipe connection 104, a nipple or middle pipe piece 105 and a lower pipe piece 106. The middle and lower pipe pieces 105 and 106 are attached with a threaded connection 107. Likewise, the upper pipe piece 104 and the middle pipe piece 105 are connected by means of the threaded connection 108. The housing 101 includes an enlarged diameter, radially expanded inner part 109 placed in the pipe pieces 104, 105 and 106.1 the lower end of the threaded connection 108 shows the pin end of the

the upper tube piece 104 an annular stop shoulder 110. An annular release profile 111 which slopes or curves radially inward to form a downwardly facing conical truncated shoulder is positioned above the extended inner portion 109. Below the stop shoulder 110, the middle tube piece 105 includes a bore 112a with extended diameter. At the lower end of the bore 112a, the middle pipe piece 105 exhibits an enlarged, annular expansion recess or groove 112b around a portion of its inner circumference. The pipe piece 105 further includes upper and lower inwardly projecting annular radial bearing surfaces 90a, 90b. The bearing surfaces 90a and 90b each form an annular shoulder where a sealing ring unit 113 is placed next to this. The sealing ring unit 113 includes a number of chevron or zigzag-shaped elastic seals with end holders. An actuator sleeve 92 is located inside the expanded inner portion 109 between the expansion groove 112b and the

upper sealing unit 113. The lower sealing unit 113 is activated with the spigot end of the lower tube piece 106 on the threaded engagement of the threaded connection 107. A number of ports 115 are positioned azimuthally around the circumference of the housing 101 between upper and lower bearing surfaces 90a and 90b. The lower tube piece 106 also includes an upwardly facing conical truncated activation shoulder 94.

The sleeve valve assembly 100 further includes a closing sleeve or sleeve valve 114 which is axially slidably received into the radially expanded portion 109 to be moved up or down to open or close the current port 115. The sleeve valve 114 forms a common current bore 96 with the switch string 76. The ports 115 inside the housing 101 is adapted to allow fluid communication from the inside to the outside of the housing 101 to occur. A number of longitudinal openings 116 are formed around the circumference of the sleeve valve 114 which, when aligned with the ports 115, allow fluid to flow from inside the fluid flow tube 96 or switch string 76 and through the ports 115 in the housing 101. The sleeve valve 114 also includes a number of longitudinal slits 117 which form collars 118.1 an exemplary, preferred embodiment, the slits are 2.5 mm wide and placed azimuthally from each other around the circumference of the sleeve valve 114 in 22 Vi° intervals. Each collar 118 includes a radially projecting element or boss 119 which projects outwardly from the claims 118 and into the radially expanded portion 109. Preferably, the boss 119 has an upwardly facing conical truncated surface 119a and a downwardly facing conical truncated surface 119b. The surfaces 119a and b are chamfered or angled at approximately an angle of 45°. In an exemplary embodiment, the boss measures 9.5 mm in height. The sleeve valve 114 includes upper and lower internal engagement depressions 120, 121. The upper engagement depression 120 has an annular downward-facing, upper force-bearing shoulder 120a and a lower upward-facing, inwardly camming conical truncated surface 120b. The lower engagement recess 121 exhibits a lower, annular upwardly facing, force-carrying shoulder 121a and an upper downwardly facing, inward camming conical truncated surface 121b.

The outer cylindrical surface of the sleeve valve 114 slidingly contacts the part of the section 109 which is located in the lower tube piece 106. The outer surface of the sleeve valve 114 also abuts the annular support surfaces 90a and 90b in the middle tube piece 105. The actuator sleeve 92 is placed between the outer cylindrical surface of the sleeve valve 114 and the inner cylindrical surface of the section 109. The sleeve valve 114 has a length that is less than the length of the section 109, which allows the sleeve valve 114 to be axially slidable within the extended portion 109 between the lower annular shoulder 95 formed in the lower tube 106 of the extended section 109 and the downwardly facing annular shoulder 96 of the upper tube 104 which forms the upper end of the extended section 109. A split ring or C-ring 122 is slidably located in the annulus formed by the outside of the sleeve valve 114 and the inner circumference of the extended section 109 of the middle pipe piece 105.1 cross-section shows the C-ring 1 22 radially inner corners 122a and 122b which are chamfered or otherwise reduced to be angled at about 45°. This feature is best understood with reference to Figure 7. The C-ring 122 is placed so that it can move axially along the bore 112a with an expanded diameter between the inwardly extending stop shoulder 110 and the expansion groove 112b. The C-ring 122 is dimensioned so that it will be tightly occupied in the bore 112a, so that the C-ring 122 is contracted and thus reduced in diameter. It must also be dimensioned so that it will be more tightly accommodated in the radial expansion groove 112b and the C-ring 122 is allowed to expand and thus be enlarged in diameter. The C-ring is initially placed close to the stop shoulder 110. The C-ring 4 22 is preferably tensioned so that it can withstand impact.

An exemplary opening switch 62, shown in Figures 2A-B and 4A-B, includes suitable upper and lower couplings 131, 132 for operative connection of the opening switch 62 in the switch string 76. The opening switch 62 has an outer keyway 134 connected to the string

76 in the upper coupling 131. The outer wedge dormer 134 has a housing part with a downwardly extending skirt 98 which has a number of wedge slots 135 and an equal number of wedge openings or windows 136 azimuthally arranged around the circumference of the skirt 98. The lower end of each wedge slot 135 is provided with an upwardly facing, inwardly combing surface 135a. The lower end of each window 136 is likewise provided with an upwardly facing, inward cambering surface 136a. The opening latch 62 also includes a tool mandrel 137 threadedly engaged therein

its upper end to the housing portion at the outer key mandrel 134. The mandrel 137 has a portion of reduced diameter near its upper end which exhibits an outwardly projecting, upwardly facing bearing shoulder 137a. When in such engagement, the portion with reduced diameter forms a wedge recess 138 between the outer key mandrel 134 and the tool mandrel 137.

A set of radially movable wedges 150 are located inside the wedge recess 138 for radial movement through the wedge slots 135 and the wedge windows 136. There are preferably four such wedges located at a 90° angle from each other around the circumference of the tool mandrel 137. The wedges 150 are externally tensioned with and elastic held away from the tool mandrel 137 by means of one or more arc springs 151. Each arc spring 151 includes a lower radially projecting lower end which is engaged in a slot in the wedge 150. The wedge recess 138 has a length which will allow the arc spring 151 to contract to a flattened position so as to be fully occupied within the wedge recess 138. A spring retaining slot 154 within the wedge 150 is arranged to receive a portion of the bow spring 151. The wedges 150 include an outwardly projecting nose or comb head 152 and an outwardly projecting square abutment shoulder 153 The cam head 152 exhibits an upwardly facing conical truncated cam surface 152a and a downwardly facing conical truncated cam surface 152b. The upper cam surface 152a is shaped to be complementary to the release profile 111. The landing shoulder 153 exhibits an upward force-carrying shoulder 153a and a downwardly facing conical truncated cam surface 153b. Each wedge recess 138 includes a movable wedge 150 with the comb head 152 protruding through the wedge slot 135 and the abutment shoulder 153 protruding through the wedge window 136. The wedges 150 are held in the wedge groove 138 with an annular sleeve 139 connected to the tool mandrel 137 with a shearable shear pin 140. As the advantageously there are four wedges 150, there are also advantageously four shear pins 140. The annular sleeve 139 includes an inwardly projecting annular radial flange 141 which lies against the lower terminating end of the wedges 150. The annular flange 141 protrudes into the wedge recess 138. The outer circumferential surface of the sleeve 139 provides an annular bearing surface for the lower end of the

■the skirt 98 of the outer keeledor 134.

In operation, the switch string 76 is moved upwards inside the production pipe string 70 something like

causes the wedges 150 in the opening switch 62 to contact the sleeve valve 114 for the purpose of moving it to the open position. When the wedge window 136 is flush with the upper engagement groove 120 in the sleeve valve 114, the arc spring 151 pushes the wedge 150 outward through the wedge window 136 and into the slot or recess 120. The upper force-bearing shoulder 153a of the shoulder 153 contacts the upper force-bearing surface 120a of the sleeve valve 114. When in contact, further upward movement of the opening switch 62 will move the sleeve valve 114 upwardly within the section 109 and into an open position, as shown in Figures 4A-4B, where the openings 216 are adjacent the ports 115 in the housing 101 to allow fluid communication between the current the ring 96 in the switch string 76 and the perforations 82 in the producing zone 85. The tensile force required to open the sleeve valve 114 should not be significantly greater than that required just to move the switch string 76 relative to the production tubing string 70. Further movement of the opening switch 62 in the upward direction causes the wedge head 152 on the wedges 150 to release the contact shoulder 153 of the sleeve valve 114 while until 114 remains in the open position. As shown in Figure 3 A, the upper cam-bearing surface 152a of the wedge head 152 contacts and is cam-guided inwardly by the release profile 111. This inward camming releases the upper force-bearing surface 153a of the square mounting shoulder 153 from the upper force-bearing surface 120a of the sleeve valve 114 which causes the opening switch 62 moves out of the housing 101 and upwards into the production pipe string 70.

When the sleeve valve 114 is open, it is desirable to position it and pump acid through it. As can be seen in Figures IA and IB, further upward movement of the switch string 76 causes the placement unit 63 to pass into the current bore 102 of the housing 101. Reference is now made to Figures 4A and 4B where the placement unit 63 is shown which is similar in construction and operating as the opening switch 62. The location unit 63 is usually located on the pipe section below the opening switch 62.1 common tool strings, a pipe section is usually about 10 m long. A difference between the opening switch 62 and the location unit 63 is that the axial distance between the wedge head 252 and the abutment shoulder 253 on the wedges 250 of the location unit 63 is less than the axial distance between the wedge head 152 and the abutment shoulder 153 on the wedges 150 of the opening switch 62. The acid treatment mandrel 52, shown in Figure IA, which contains the side ports 67 is engaged in the lower coupling 232. The side ports 67, the longitudinal openings 116 and the ports 115 together form a passage to the perforation 82. When force is applied to the positioning assembly 63 to move it upwardly in the front to the house.. 101; causes the reduced axial length of the boss 119 of the sleeve valve 114 to abut the C-ring 122 which is inside the enlarged diameter bore 112a. Corner 122a of C-

the ring 122 contacts the surface 119a of the boss 119. Each collar 118 and boss 119 can then be characterized as a stop element that blocks the passage of the positioning unit 63

upwards past the location of the sleeve valve assembly 100. The sliding sleeve valve 114 and the contact

tending placement unit 63 is releasably retained inside the housing 101.

When retained, the acid treatment can be carried out with acid sent into the perforations 82 in the producing zone 85 through the passage formed by the side ports 67, the longitudinal openings 116 and the ports 115.

Upon completion of the acid treatment operations, the placement unit 63 can be released

by means of increased axial force on the shift string 76. When increasing tensile force is applied to the shift string 76 and the positioning unit 63, the claims 118 are forced radially inward to a degree sufficient to overcome the retention by allowing the C-ring 122 to pass under the bos-

set 119 on each collar 118. A sufficient magnitude of the tensile force will force the claims 118 radially inward so that the boss 119 can move past the C-ring 122. Chamfering, chamfering or other reduction of the complementary engagement surfaces 122a and 119a to e.g. . 45° angles assist the movement of the boss 119 past the C-ring 122 by substantially cambing the boss 119 radially inward toward a radially contracted position. This chamfer, as shown in Figure 7, also prevents a rigid locking type joining of the C-ring 122

and the boss 119 which would cause the location switch 63 to become permanently stuck.

The force required to move the boss 119 past the C-ring 122 can be determined by a weight indicator on the surface. The retention can be overcome by applying a significantly greater tensile force to the shifting string 76. To ensure that it is clear that the shifting tool has been retained, the tensile force required to overcome the retention is usually at least twice the normal force required to move the shifting string 76 relative to the production tubing string 70 in an unrestrained state. In an exemplary embodiment, a force of approximately 1000 kp, which corresponds to a large extent to the frictional forces provided by the sealing elements inside the housing, may be necessary to move the switching tool inside the housing.

A tensile force of approximately 15,000 kp or more may be necessary to loosen the shearing tool.

The rapidly increasing resistance to upward movement of the shift string 76 associated with retention of the positioning unit 63 on the C-ring 122 serves a positioning function and a signaling function. The positioning function ensures that the side flow ports 67 in the acid treatment mandrel 52 are located close to the ports 116 in the sleeve valve 114 and that the sleeve valve 114 is in its open position so that stimulation fluid can be sent through the flow bore 96 in the switching string 76 and correctly positioned in the perforations 82. The device functions as a signal by giving a positive indication to operators on the surface that the sleeve valve 114 is opened and that the acid treatment mandrel 52 is correctly positioned. The signaling function is valuable in applications such as acid processing operations where the acid is correctly and safely passed into the flow pipe only after the sleeve valve 114 has been opened and the tool has been correctly "positioned". Testing has shown that the tensile force on the shear string 76 will increase in the order of magnitude from approximately 12,500 to approximately 17,500 kp. During the acid treatment, sufficient tensile force, usually 7500 to 9000 kp, should be maintained on the inner string so that the boss 119 is known to engage the C-ring 122 and yet not enough tensile force should be applied to cause the boss 119 to slip past the C-ring 122 .

The upwardly directed tensile force on the switch string 76 is maintained throughout the stimulation operation. This provides a constant indication that the acid processing mandrel 52 is close to the ports 115 and that the seals 61 are tightly engaged with the seal bores above and below the housing 101. When stimulation fluid, such as acid, is passed down the switch string 76, the colder stimulation fluid causes the switch string 76 to pull themselves together. When the switch string 76 contracts, the tensile force on the switch tool 60 is measured with a weight indicator on the surface. A predetermined amount of tensile force is maintained on the switching tool when the acid is pumped. The tensile force can be reduced to counteract the contraction length of the switch string 76. Thus, when the switch string 76 contracts, the tension on the switch tool 60 is reduced to ensure that the seals 61 remain in the seal bores and that the acid treatment mandrel 52 is close to the ports 115. If the sleeve valve is to remain open, release the boss 119 past the C-ring 122 and the switch string continues to be pulled upwards. The shut-off switch 64 will pass the sleeve valve 114 in an upward direction because there are no upwardly facing square rods on the wedges 350 of the shut-off switch 64 to contact the upper engagement recess 120 or lower engagement recess 121 of the sleeve valve 114. The shut-off switch is usually located on the length of pipe below the location assembly. The opening switch 62 and the positioning unit 63 can then be moved upwards to a separate stimulation zone where, through the same opening and positioning operation, that zone can be acid treated. The described retaining feature allows optional placement of the placement unit 63 and the sleeve valve inside the housing 101.

If it becomes necessary to reverse the direction of the switching tool 60 in order to place it downwards in the housing 101, this can be carried out without closing the sleeve valve 114 and without bumping into the 60 being moved upwards..., ,

-relation to-housingV-Fi^ Note that the boss 119 is located above the C-ring 122. Movement of the switch tool 60 down-

ad in relation to the housing 101 will cause the boss surface 119b to contact the corner 122a of C-

the ring 122 and slide it axially downwards along the inside of the housing 101 until it reaches the annular expansion groove 112 and expands radially into the groove 112. In case of radial expansion outwards into the groove 112, the C-ring 122 will be moved outwards from blocking the boss 119

so that no significant retention will occur. In the typical case, the additional force required to move the C-ring 122 into the expansion groove will amount to approximately 50 kp in additional downward force.

After release under tension, the switch string 76 may continue to be pulled upward to

either to continue acid treatment in another producing zone or to remove the switch string from the tubing string 70. When the switch string 76 is removed, the well control valve switch 65 will pass and slide the slide sleeve valve which activates the poppet valve 75 and causes it to close. If in an emergency it becomes necessary to close the sleeve valve 114

the surface operator can do this by pulling the switch string 76 upwards until the closing switch 64 is located inside the sleeve valve 114 near the engagement groove 121 and the shoulder 121a. The closing switch 64 can then be moved in a downward direction relative to the housing 101

to close the sleeve valve 114. The closing switch 64 is also constructed and operates the

me as the opening switch 62 in most respects. However, as shown in Figures 6A and B, the components of the closing switch 64 are reversed in direction. The wedges 350 in the closing switch 64 are engaged in the lower engagement recess 121 instead of in the upper engagement recess 120. In the manner described for the opening shutter 62, the closing switch 64 contacts the sliding sleeve valve 114 and moves it towards its closed position and disengages from the sleeve valve 114 with the wedge 350 which is cam-guided against the shoulder 94.

If the sleeve valve 114 becomes stuck so that it cannot move axially, emergency release of the opening switch 62, the closing switch 64 or the positioning unit 63 can be carried out. While an exemplary release of the opening switch 62 will be described, it is pointed out that the release of the positioning unit 63 and the closing switch 64 are similar in most respects. Release of the wedges 150 from the sleeve valve 114 can be performed by pulling or striking upwards on the outer wedge mandrel 134 via the shift string 76. The pulling or knocking will stress the pin 140 in shear between the tool mandrel 137 and the annular sleeve 139. By cutting off the pins 140, the skirt 98 allows to move upwards relative to the wedges 150 and cam the wedges 150 inwards due to the engagement with the cam surface at 97. By cutting off the tabs 140 the skirt 98 is allowed to move upwards relative to the wedges 150 and cam the wedges 150 inwards due to the engagement with the comb faces at 97 and between 152b and 135a. A further upward pull in the outer wedge mandrel 134 will then cause the wedges 150 to contract radially when the wedges 150 are cammed inwards at 97 as well as along the surface 152b at the surface 135a, respectively, which thus loosens the upper force-bearing surfaces 153a and 120a. It should be noted that the cutting pin 140 should be a sufficiently strong member so that it will cut away only in response to a substantially higher force than that which would be required to push the boss 119 past the C-ring 122. It is contemplated that the tool and devices of what is described here has useful application for horizontal or deviated wells. It should therefore be noted that the directions such as up/down and upper/lower can be interchanged with in/out etc.

Although the invention has been described with respect to certain preferred embodiments, it is obvious to those skilled in the art that it is not limited thereto. The sleeve valve and the placement arrangement, as well as the operation of these as described here, can be used for perforating, fracturing or other operations. The closed and open positions of the sleeve valve can e.g. reversed or the wedges or other components of a switch may be differently designed

Claims (1)

- H<y>lsévéntiléhét^(72) device-for incorporating into a well flow guide pipe=and-controlling-fluid-~-" "w the flows from the flow guide pipe at a predetermined position in the flow guide pipe, comprising a generally cylindrical outer housing (101), said housing having an interior surface (103) forming an internal fluid flow conduit (102) and also having a port (115) for fluid communication through said housing; a sleeve valve (114) placed inside the housing (101) and axially slidable therein between a first position and a second position, characterized by a radially expanded portion (109) along the inner surface of the housing, which radially expanded portion exhibits an inwardly extending stop shoulder (110) at a point along its length, where the sleeve valve is longitudinally slotted (117) along a portion of its length to form a number of collars (118) within the sleeve valve (114); a boss (119) projecting radially outward from a location on at least one of the claims into the radially expanded section; a reduced diameter bore located radially outside the sleeve valve within the radially expanded section; and a split ring (122) slidably positioned within the reduced diameter bore so that, when the sleeve valve (114) is moved axially toward the first position, the boss (119), the split ring (122) and the stop shoulder (110) contact each other so that the sleeve valve becomes releasable retained against further axial movement towards the first position. 2. Sleeve valve unit according to claim 1, characterized in that the sleeve valve (114) can be released from the restraint by applying increased axial force to move the sleeve valve towards the first position so that the boss (119) escapes axially past the splitting ring (122). 3 Sleeve valve assembly (72) adapted for incorporation into a well flow guide pipe and controlling the fluid flows from the flow guide pipe at a predetermined position in the flow guide pipe, comprising a generally cylindrical outer housing (101), which housing has an internal surface (103) which forms an inner fluid flow pipe (102) ) and which also has a port (115) for fluid communication through the housing; a sliding element placed inside the housing (101) so that it is axially slidable in it between a first position and a second position, characterized in that the sliding element (114) is longitudinally slotted (117) along part of its length for forming a plurality of collars (118) within the sliding member (114), the sliding member being movable to its first position in response to a first axial shifting force and movable to its second position in response to a second axial shifting force that is greater than the first axial shear force. 4. ..Sleeve attachment device.according to c a r a c t e r i,s e.r t. w e d .. at. the first axial shifting force is approximately 907 kp and the second axial shifting force is approximately 13608 kp. 5. Flow control device for controlling the fluid flows from a flow conduit at a predetermined position in the flow conduit, comprising a substantially cylindrical outer housing (101) with a side port (115) adapted for fluid communication; a sleeve valve unit (100) which is included in the housing (101), where the sleeve valve unit comprises a sleeve valve (114) arranged in the housing (101) and is axially slidable therein between a first position and a second position, and is operable to optionally open and close the side port (115) in the housing, and includes a switching tool (60) which can be inserted into the housing (100) and be axially movable therein, and a switch (62) which is operable to contact the sleeve valve (114) to moving the sleeve valve toward its first position and releasing the sleeve valve; characterized by a radially expanded section (109) along the inner surface of the housing, said radially expanded section having an inwardly extending stop shoulder (110) at a location along its length; wherein the sleeve valve is longitudinally slit (117) along a portion of its length to form a number of collars (118) within the sleeve valve; a boss (119) projecting radially outward from a location on at least one of the claims into the radially expanded section; a split ring (122) which is slidably arranged in the radially expanded section so that, when the sleeve valve (114) is moved axially towards the first position, the boss (119), the split ring (122) and the stop shoulder (110) contact each other so that the sleeve valve (114 ) is releasably restrained against further axial movement towards the first position; and a positioning unit (63) included in the switch tool (60), which positioning unit is operable to contact the sleeve valve and cause the sleeve valve (114) to be held against further axial movement toward the first position. 6. Flow control device according to claim 5, characterized in that the sleeve valve (114) comprises a radially internal engagement recess which exhibits a force-carrying shoulder and that the switch (62) comprises a radially expandable wedge which has a bearing surface arranged to contact the force-carrying shoulder of the sleeve valve (114) which thus contacting the switch with the sleeve valve. 7. Method for stimulating an underground formation through a borehole with , a stimulation fluid, comprising a sleeve valve (414) and a switch string (76) inside the pipe string (70), wherein the switch string includes at least one switch (62); axially moving the switch string (76) within the tubing string in a first direction until a switch (62) on the switch string contacts and moves a sliding sleeve in the sleeve valve (114) to open ports in the sleeve valve (114) for access to the formation; sending stimulation fluid through the stimulation tool (40) and the ports and into the formation; characterized by further moving the switch string (76) in the first direction until a positioning device (63) on the switch string contacts the sleeve valve; applying a first increased axial force on the switch string in the first direction to carry the positioning device (63) against a stop member (110) on the sleeve valve to ensure that a stimulation tool (40) in the switch string is close to the ports and the formation; after sending the stimulation fluid into the formation, applying a second increased axial force greater than the first axial force to the switch string (76) to urge the placement device (63) past the stop member. 8. Method according to claim 7, characterized in that it includes movement of the switch string (76) in a second direction opposite the first direction and contacting the sleeve valve (114) with another switch (64) on the switch string to close the sleeve valve.